This section provides background information related to the present disclosure which is not necessarily prior art.
PEPS systems allow a vehicle to locate a key associated with the vehicle, such as a wireless key fob carried by a user of the vehicle. Traditionally, PEPS systems allow anyone in possession of a key fob that has been previously paired with a vehicle's central PEPS electronic control unit (ECU) to access the vehicle by simply grabbing the door handle and to start the vehicle with a push of a button. In response to a button push, the central PEPS ECU authenticates the key fob to determine if the key fob is authorized to access the vehicle and uses the signal strength indicated by a plurality of vehicle antennas to estimate the location of the key fob. If the key fob can be authenticated and is located within an authorizing zone, the vehicle's function is made available to the user, i.e. the vehicle doors are unlocked and/or the vehicle is started.
Traditional PEPS systems use proprietary grade radio protocols using low frequency (LF) signals of approximately 125 kHz. LF was selected for early PEPS systems because the wave propagation would allow for relatively accurate estimation of range and location by using signal strength within the typical target activation range of 2 meters. The LF communication systems used with traditional PEPS systems, however, use fixed frequencies for communication and do not implement any frequency hopping scheme or any encryption of communication packets.